Electric baseboard heaters



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Sept. 30, 1969 H. c. FISCHER 3,

ELECTRIC BASEBOARD HEATERS Filed March 22, 1965 a Sheets-Sheet 4 INVENTOR. I

p 0 969 H. c. FISCHER 3,470,351

ELECTRIC BASEBOARD HEATERS Filed March 22, 1965 8 Sheets-Sheet 5 Sept. 30, 1969 H. c. FISCHER 3,470,351

ELECTRI C BASEBOARD HEATERS Filed March 22, 1965 8 Sheets-Sheet 6 V INVENTOR. HARRT C. Fsscuzca A rrarrwe s Sept. 30, 1969 H. c. FISCHER 3,470,351

ELECTRIC BASEBOARD HEATERS Filed March 22, 1965 8 Sheets-Sheet 7 J 37 1; "Wm U 'T l 5': $75 7,7 gvfi 5 .1 s

INVENTOR.

HARRY C- FscHER Sept. 30, 1969 c. FISCHER 3,

ELECTRIC BASEBOARD HEATERS Filed March 22, 1965 8 Sheets-Sheet KM a MIMI!!! .r g E m mm 7 54 INVENTOR, HARRY C. FwcHzR' BY United States Patent 3,470,351 ELECTRIC BASEIBOARD HEATERS Harry C. Fischer, Royal Oak, Md., assignor to Edwin L. Wiegand Company, Pittsburgh, Pa. Filed Mar. 22, 1965, Ser. No. 441,643 Int. Cl. H051) 3/02 US. Cl. 219366 23 Claims ABSTRACT OF THE DISCLOSURE A baseboard heater free of internal bafile means, including a heater wire doubled on itself to form a plurality of reaches, and bight portions at opposite ends of the reaches and defining the ends of the heating element. The wires in each bight portion extending about rotatable dielectric bushings to provide a multiple-sheave block and tackle elfect. Spring means hold the heater wire taut and also provide for electrical connection thereto. The heater also includes a bottomless plenum chamber and a thermally responsive device in electric circuit with the heater wire and disposed within the plenum chamber to reduce heat output of the heater wire upon excessive temperature rise Within the chamber.

The present invention relates to baseboard heaters, particularly of the electric resistance type and to methods of controlling and assembling the same, and the principal object of the invention is to provide new and improved devices and methods of the character described.

Although many electric resistance baseboard heaters have been devised, none has met with the anticipated commercial acceptance for several reasons. Firstly, the high operating temperature of the elements of most baseboard heaters has necessitated the use of various internal baflles to prevent the heater casing from reaching excessive temperatures. These baflles, however, and other parts of the assembly, including the element itself, constitute a restriction to air flow through the heater and such restriction, with the accompanying high operating temperature of the element, causes high temperature air to be discharged at high velocities from the heater. These high temperatures and velocities have been a primary cause of wall-streaking above the heater. Secondly, the

use of various baflles increases the number of parts and adds to manufacturing costs and ultimately in higher cost to the purchaser.

In contrast, the present invention provides a baseboard heater assembly having a low temperature heating element and no internal bafiles to restrict air flow through the heater. Thus, such novel heater discharges air at low velocity and at low temperatures thus resulting in a safer unit and one which minimizes wall streaking. Moreover, the present invention provides a baseboard heater which is simple in construction, readily assembled without skilled labor, and thus can be manufactured at lower costs. These and other advantages will readily become apparent from a study of the following description and from the drawings appended hereto.

In the drawings accompanying this specification and forming a part of this application there is shown, for purpose of illustration, embodiments which the invention may assume, and in these drawings:

ice

FIGURE 1 is a perspective view of a preferred embodiment of a baseboard heater assembly constructed in accordance with the teachings of the present invention;

FIGURE 2 is an enlarged, front elevational view of the assembly, certain parts on the near side being removed to show the underlying structure,

FIGURE 3 is an enlarged sectional view generally corresponding to the line 3-3 of FIGURE 2,

FIGURE 4 is an enlarged view, similar to FIGURE 2, but of only the left end of the parts there shown and with one part removed to show the underlying structure,

FIGURE 5 is an enlarged, broken perspective view of a detail seen in FIGURES 2 and 4,

FIGURES 6 and 7 are fragmentary sectional views generally corresponding to respective lines 66 and 7-7 of FIGURE 4,

FIGURE 8 is a view similar to FIGURE 4 but showing certain of the parts at an earlier stage of assembly,

FIGURE 9 is an enlarged, fragmentary elevational view of a detail, parts on the near side being broken away to show the underlying structure,

FIGURE 10 is a view generally corresponding to the line 1010 of FIGURE 9,

FIGURE 11 is a reduced size perspective view of a detail seen in FIGURES 4, 9 and 10,

FIGURE 12 is an enlarged, fragmentary view of a portion of the device seen in FIGURE 2,

FIGURE 13 is a view similar to FIGURE 12 but showing a detail at an earlier stage of assembly,

FIGURE 14 is an enlarged perspective view of a detail seen in FIGURE 2,

FIGURE 15 is an enlarged, exploded, fragmentary view generally corresponding to the line 15-15 of FIGURE 1,

FIGURE 16 is a fragmentary view similar to FIGURE 9 but of another embodiment, and

FIGURE 17 is a fragmentary view similar to FIGURE 9 but of still another embodiment.

With reference to FIGURE 1, the present invention relates to a horizontally elongated heater assembly adopted to be installed at the junction of the floor and a wall of a room to be heated. Since the present type of device normally occupies the place in which the baseboard is mounted, it is commonly referred to as a baseboard heater. As in the usual case, the present device takes the form of a horizontally elongated housing having a rear wall 10 adapted to abut a wall of the room to be heated, a lower wall 11 adapted to abut the floor of such room, an upper wall 12 spaced above the lower wall 11, and a forwardly projecting front wall whose intermediate portion 13, or grille, is perforated or is otherwise formed to enclose the housing interior while providing for free flow of air into and out of the housing.

As best seen in FIGURE 3, the heater assembly housing is in part provided by an elongated sheet metal member 14 formed to a channel-like configuration whose web portion provides the rear wall 10 and whose flange portions provide respective lower and upper walls 11 and 12. Still referring to FIGURE 3, one end of housing member 14 is closed by a terminal housing 15 while the opposite end of the housing member 14 is closed by a terminal housing 15.1 (FIGURE 2). Since terminal housings 15, 15.1 are identical with the exception that they are of opposite hand, a detailed description of only terminal housing 15 should sufiice. Where shown, corresponding parts of the terminal housing are identified by the same reference characters but with the parts of housing 15.1 carrying the suflix .1.

With reference to FIGURE 5 and with the understanding that the terminal housing closely fits between the main housing member lower and upper walls 11, 12, such terminal housing has a rear wall 16 adapted to overlie the main housing member rear wall 10 and a lower wall 17 adapted to overlie the main housing member lower wall 11. Extending forwardly of terminal housing rear wall 16 are spaced, outer and inner end walls 18, 19 each having a forwardly protruding, fiat central portion 20 and slightly concaved upper and lower portions 21 and 22, respectively. For a purpose to appear, inner wall 19 is split to provide spaced portios 23, 24 extending toward the outer wall 18 and providing respective, outwardly directed slide surfaces 25, 26 in side-by-side relation. The upper and lower ends of inner wall 19 are cut away at 27 and 28, and inwardly extending aligned tabs 29 and 30 are respectively provided by wall 19 thereat for a purpose to appear.

Novel means are provided for securing the terminal housing 15 in the end of the main housing member 14 and with reference to FIGURES 4, 5 and 8, rear wall 16 of the terminal housing is cut away to provide upper and lower tongues 31 and 32 which face inwardly or toward the inner wall 19. Cooperating with the tongues 31, 32 are loops 33, 34 formed in the rear wall 10 of the main housing member 14 by a lancing operation. As best seen in FIGURES 4, 6, 7 and 8, such loops closely receive respective tongues as the terminal housing 15 is slid into the main housing member 14 as indicated in the partically assembled view FIGURE 8. Note especially that interengagement of the tongue and loops aforesaid limits inward movement of the terminal housing with respect to the main housing member and maintains the rear wall 16 of the terminal housing tightly against the rear wall 10 of the main housing member.

Still referring to FIGURE 5, terminal housing walls 16, 17 and 18 are provided with the usual knockouts 35 which may readily be removed for the passage of wiring or the like. Clearly, with respect to the knockouts in walls 16 and 17, the corresponding walls of the main housing member are apertured in registry therewith. Also, and for reasons to appear, terminal housing walls 18 and 19 are provided with facing lugs 36 and 37 having threaded apertures for receiving certain fastening members. Finally, and with reference to FIGURES 4 and 8, the terminal housing and the main housing member are provided with registering slots 38 and 39 for passing a suitable fastening member which secures the assembly to the wall of the room. Note that passage of a fastening member through the registering slots 38, 39 effectively prevents disassembly of the terminal housing from the main housing member.

As best seen in FIGURE 2, a novel electric resistance heating element assembly 40 extends between the inner walls 19, 19.1 of the terminal housings 15, 15.1 in a manner later to appear. Element assembly 40, and with reference to FIGURES 9 and 10; comprises two banks 41, 42 of resistor conductor wires which are preferably identical. The wire banks 41, 42 are disposed in side-byside relation with the wires of each wound upon respective, spaced pins 43, 44. In order to insure electrical isolation between the bight portion of each wire strand and the pins, a plurality of dielectric, peripherally grooved bushings 45 are strung upon the pins with each wire strand bight portion disposed in a respective bushing groove. For a purpose to appear, all of the bushings 45 are rotatable about their respective pins.

Each pin 44 has a flanged, dielectric bushing 46 at respective ends and each bushing 46 mounts a flanged metallic sleeve 47. The wire ends of each wire bank 41, 42 are twisted to form loops disposed about respective sleeves 47 for anchoring such wire ends in position, any

insulating covering or the like on the wire end loops being removed to insure electrical continuity between the wire ends and the respective metallic sleeves 47.

Novel means are employed for mounting the pins 44 to a dielectric terminal block 48 and such means presently comprises a helical spring 49 for respective ends of each pin 44. Each spring 49 has loops 50, 51 at respective ends thereof, each spring loop 50 being disposed about and in electrical continuity with respective sleeves 47 A suitable retainer 52 has frictional engagement with respective sleeves 47 to prevent unintentional disassembly of the wire end loops and the springs loops 50 from the sleeves 47. Spring loops 51 extend through slots 53 formed in the terminal block 48 (see also FIGURE 11) and are retained therein by terminal lugs 54 of lead wires 55 which span respective block slots 53 and project through the spring loops 51 to prevent withdrawal thereof. Clearly, so long as the springs 49 remain tensioned, the lugs 54 will prevent disassembly of the springs from the block and will simultaneously establish electrical connections from their attached lead wires to the springs. For reasons to appear, opposite edges of terminal block 48 have rabbets 56.

The means for anchoring the pins 43 to a dielectric terminal block 57 which is similar to block 48 comprises a yoke 58 having spaced legs 59 formed with pockets 60 in which respective pin ends are received. Screws 61 extend through block 57 and have threaded engagement with the yoke 58 to vary the spacing between the latter and this block. Block 57 has rabbets 62 similar to rabbets 56 of block 48 and although not shown, blocks 48, 57 may, if desired, be identical with each providing the slots for passing the spring loops 51 and apertures for passing the screws 61 so that either terminal block can be used at either end of the element assembly.

The heating element assembly seen in FIGURES 9 and 10 will be assembled as illustrated with the terminal blocks 48, 57 maintained in separated relation to keep the springs 49 and thus the resistor conductor wires 41, 42 under tension. The heating element assembly will then be assembled with the main and terminal housings previously described by sliding the rabbets of terminal block 48 along respective surfaces 25, 26 of the terminal housing wall portions 23, 24 of terminal housing 15 and by sliding the rabbets of terminal block 57 along the corresponding portions of the terminal housing 15.1 until respective terminal blocks abut respective terminal housing rear walls 16, 16.1. If required, screws 61 can be rotated to increase or decrease the tension on the wire banks 41, 42, it being understood that the screws 61 should be so adjusted that the wire banks will at all times be tensioned at least a small amount to prevent sagging of any of the strands thereof. Finally, cover members 163 such as shown in FIGURE 14, may be slipped over the wall portions 23, 24 of terminal housing 15 and the corresponding portions of terminal housing 15.1, as seen in FIGURE 2, to protect the springs 49 and to impart a symmetrical, finished appearance.

With the construction as thus far described and when electrical energy is passed through the resistor conductor wire banks 41, 42, from the lead wires 55, the wires of the wire banks will become hot. This will produce a convective air flow wherein cool air will enter the main housing through the lower portion of the perforated front wall or grille 13 and exit from the housing through the upper portion of the grille 13. In passing over the hot wire banks the air will absorb heat from the wire banks in the usual manner.

As the wire banks become heated, the strands thereof will increase in length in accordance with well-known principles; however, such strands will be maintained under tension at all times by the pull exerted by the springs 49. Accordingly, with an increase in the total length of the wires forming the wire banks 41, 42, pin

44 will move to the left (FIGURE 9) under the urging of the springs 49. During movement aforesaid of the pins 44, the action of the wires forming the wire banks and their bushings 45 is not unlike a multiple sheave block and tackle, the bushings 45, being individually rotatable on their respective pins, freely permitting movement of individual wire strands in a longitudinal direction and about respective bushings.

Since air in passing over the heating banks cools the resistor conductor wires, any interruption in the flow of such air, caused perhaps by an obstruction against the grille 13, could result in a damaging and dangerous high temperature rise. To prevent this high temperature rise, the following structure is employed.

As best viewed in FIGURES 2 and 3, a metal strip 63 extends between the terminal housings 15, 15.1 and rests upon the forwardly facing surfaces of the terminal housing tabs 30. Strip 63 thus cooperates with the rear and upper walls 10 and 12 of the main housing to provide an elongated plenum chamber 64 having a downwardly facing opening.

The means for securing strip 63 in place presently comprises a pair of brackets 65 spaced longitudinally of the heater as shown in FIGURE 2. Each bracket 65 has a body portion 66 lying against and secured to the main housing rear wall 10 and a leg portion 67 overlying and abutting the strip 63. Preferably, the upper margin of the strip is doubled back on itself at 68 to form a channel in which the free end of bracket leg 67 is disposed to retain the strip closely against the main housing top wall 12. Bracket 66 also has a leg 69 in opposed relation to leg 67 for engaging and retaining a tubular wire way 70 which extends between the terminal housings 15, 15.1 and through which power supply or other wiring may be passed from end to end of the heater assembly.

As best seen in FIGURES 2, l2 and 13, bracket body 66 has a portion providing a lower tongue 71 and an upper tongue 72. Lower tongue 71 closely fits within a loop 73 formed by a struck out portion in the main housing rear wall 10 (similar to the previously described loops 33, 34) while tongue 72 fits beneath a tab 74 also struck from the rear housing wall.

Assembly of the brackets 65 with the main housing member 14 to retain both the strip 63 and the wire way 70 in position will readily be understood from a study of FIGURE 13. As therein shown, each bracket will be disposed in an angular position and its tongue 71 slid downwardly through the loop 73 while rotating the bracket to engage its tongue 72 beneath the tab 74.

Mounted within the previously mentioned plenum chamber 64 and, in the present embodiment, at a place midway between the terminal housings 15, 15.1, is a normally closed thermally responsive switch 75 (FIG- URE 2) having lead wires 76 (FIGURE 3) extending into the terminal housing 15. A suitable clip 77 may be employed to secure the switch 75 to the strip 63.

Assuming switch 75 to be properly connected in circuit with the resistance wire banks 41, 42, operation thereof will be as follows: During normal operation of the heater, switch 75 remains closed to energize the heater wire banks thus generating a uniformly rising flow of air. Now, since the plenum chamber is open only at the bottom, the uniformly rising air will merely flow past the plenum chamber so that the air therewithin tends to become stagnant. It is believed that the air within the plenum chamber remains stagnant because the rising flow of air, being uniform from end-to-end of the plenum chamber, exerts an even pressure on its open lower end and thus little of the heated, rising air enters the chamber.

If, however, the upward fiow of air becomes non-uniform from end-to-end of the plenum chamber, caused perhaps, by an obstruction of air flow anywhere along the heated section of the assembly, the even pressure along the chamber mouth no longer exists and with an uneven pressure thereat, a flow of air longitudinally of the plenum chamber occurs. With air flowing longitudinally of the plenum chamber, hot air rising from the wire banks enters the plenum chamber and flows therealong and, acting upon the switch 75, trips the latter to de-energize the heater wire banks. As the switch 75 cools, it will once again energize the heater wire banks until such time as non-uniform flow of air once again occurs.

Experimentation has shown that the aforesaid longitudinal flow of air along the plenum chamber will occur for a distance of about 15 inches on either side of an obstruction. Thus, a single thermally responsive switch can be used in a heater assembly having up to 30 inches of heated length to detect an overheat condition anywhere along such heated length. Where the heated length of a heater assembly is greater than 30 inches, two or more thermally responsive switches will be spaced longitudinally therealong, each switch then functioning as previously described.

As best seen in FIGURE 3, grille 13 has flanged edge portions slidably fitting between the lower and upper main housing walls 11, 12, respectively, and end portions closely fitting between the inner walls 19, 19.1 of the terminal housings (FIGURE 15). Closing the forward sides of the terminal housings 15, 15.1 are covers 77 secured to respective housings by screws 78 threaded into terminal housing lugs 36, 37. As illustrated in FIGURE 15, covers 77 are of width to overlie respective ends of grille 13 to retain the latter assembled with the main housing member.

With the construction thus far described, each heating wire bank 41, 42 forms a single heating circuit although, of course, such wire banks can be connected together in series relation into the same circuit if desired. Under certain circumstances, it may be desirable to divide one or both of the heating wire banks 41, 42 into separate heating circuits and as shown in FIGURE 16 whesein similar parts are identified by the same reference characters as before but with the suflix a added, this may be accomplished by substituting for one of the dielectric bushings 45a on pin 43a, an electrically conductive bushing 79. The heating wire portion engaging this bushing 79 will be stripped of insulation (if present) so that such wire portion will be in electrical engagement with the bushing, the pin 43a, the yoke 58a, and the screws 61a. An electrical lead 80 may underlie the head of one of the screws 61a thus providing (in this instance) a center tap for the heating wire.

In the embodiment of the invention seen in FIGURE 17, wherein similar parts are identified with the same reference characters as before but with the sufiix b added, there is illustrated a thermal cut-out arrangement which may be supplemental to that previously described or which may alternatively be used.

Recalling that the previously described springs 49 maintain the heating wire banks taut despite an increase in overall wire length caused by heating of the wires as electrical energy is passed therethrough, it will be noted in FIGURE 17 that a limit switch 81 will be carried in this embodiment by the block 48b with its actuator 82 positioned for engagement by one of the pins 44b. In normal operation, pin 44b remains spaced from the switch actuator 82. When an overheat condition occurs, however, greater than normal elongation of the heating wire bank will, under the pull of the springs 4%, cause movement of the pin 44b far enough to the left (in the position of parts shown) to engage the switch actuator 82 to open the contacts of switch 81 and to thus interrupt flow of elecrical energy to the heating wire.

A manual reset button 83, preferably accessible from the exterior of the heater housing, may be employed to reset the switch 81 for re-energization of the heating wire. Alternatively, the switch actuator 82 may be springbiased to the position shown in FIGURE 17 so that after an overheat de-energization as above mentioned, re-energization of the heating wire will automatically occur when it has contracted sufliciently to move the pin 44b to the right away from the switch actuator. This would, of course, cause intermittent energization of the heating wire until the cause of the overheat is corrected.

While but a single switch has been described for controlling one of the heating wire banks, the switch actuator could carry a bridging element which would make the actuator responsive to movement of both pins 44b. Moreover, if desired, separate switches 81 could be employed for controlling operation of respective wire banks.

In view of the foregoing it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiments herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiments are illustrative only, and that my invention is not limited thereto.

I claim:

1. A baseboard heater assembly, comprising an elongated housing, an electric heating element mounted lengthwise in said housing and adapted to be connected to an electrical power circuit, said heating element comprising an elongated heating Wire doubled back on itself to provide a plurality of reaches in side-by-side laterally spaced relation and bight portions at opposite ends of said reaches, means at said bight portions to support said heating element and to anchor the ends thereof to laterally spaced parts of said housing, one of said means comprising a metal pin on which a plurality of peripherally grooved dielectric bushings are disposed in end-to-end relation, the wire in the bight portion at said one means extending about respective bushings and disposed in the grooves thereof, an electrically conductive sleeve secured to but electrically insulated from one end of said pin, one end of said heating wire being looped about said sleeve for electrical continuity therebetween, a helical spring having an end looped about said sleeve and its other end connected to a housing part, said spring being adapted to be electrically connected to a power circuit and maintaining the heater reaches taut and also establishing an electrical connection to said one end of heating wire, and lead means connected to the other end of said heating Wire to complete the circuit thereto.

2. The construction of claim 1 wherein an electrically conductive sleeve is secured to each end of said pin in electrical isolation therewith, wherein respective ends of said heating wire are looped about respective sleeves for electrical continuity therebetween, and wherein there are two springs, each looped about a respective sleeve to establish electrical connections to respective heating wire ends and to exert a transverse force on said pin thus maintaining said wire reaches under constant tension.

3. The construction of claim 2 wherein the inner end of each sleeve is radially outwardly flanged to provide a shoulder and wherein a retainer is removably secured to the outer end of each sleeve with wire ends and the spring loops on respective sleeves trapped between said retainer and saidshoulder.

4. A baseboard heater assembly comprising an elongated housing, a pair of supports carried by and spaced longitudinally of said housing, an elongated electric heating element mounted in said housing and adapted to be tensioned between said supports, said element being formed of an elongated heating wire doubled back on itself to provide a plurality of reaches in side-by-side, laterally spaced relation joined by respective bight portions, means disposed in the bight portions aforesaid at each end of said element for supporting respective reaches and for anchoring said element ends to respective supports such means comprising a metal pin on which a plurality of peripherally grooved dielectric bushings are jonrnaled in end-to-end relation and each wire bight portion extending about a respective bushing and being disposed in the groove thereof, electrically conductive sleeves secured to but in electrical isolation from respective ends of the pin at one end of said element and respective ends of said heating wire being looped about respective sleeves for electrical continuity therebetween, means for maintaining tension on said element despite expansion and contraction thereof and comprising a pair of helical springs having a loop at each end lying in a plane generally normal to the pin axis, each spring having one end looped about a respective sleeve to establish an electrical connection therewith and with respective heating wire ends, a dielectric body interposed between said one element end and its support and having spaced slots through which respective loops at the other ends of said springs project, lead Wire means from an electrical power source extending through respective spring loops at said other spring ends and maintained therein by the tension exerted by said springs to prevent unintentional withdrawal of said spring loops from said slots and to establish electrical power circuit connections to said springs, and means anchoring the pin at the other end of said element and consequently such other element end to its support aforesaid.

5. The construction of claim 4 wherein said last-mentioned means provides for shifting of said other element end pin toward and away from its support to vary the stress on said springs and to thus vary the tension on said element.

6. The construction of claim 4 wherein one of the bushings on said other element end pin is electrically conductive, wherein the heating wire bight portion passing about such bushing is in electrical engagement therewith, and wherein means provides for connection of the electrical power circuit to said other element end pin whereby different portions of said element may be disposed in different electrical circuits.

7. The construction of claim 4 wherein said last-mentioned means comprises a dielectric body and wherein both of said dielectric bodies have sliding engagement with respective supports to facilitate assembly of said element with said housing.

8. A baseboard heater assembly, comprising a housing provided by an elongated channel member whose web portion forms a first wall and whose flange portions form spaced second walls projecting from one side of said first wall, a pair of ways on said housing and spaced longitudinally thereof and projecting from the same side of the first "wall as do said second walls, a flexible elongated electric resistance element within said channel member and adapted to be connected to a power circuit, a dielectric body at each end of said element and having connection therewith, said bodies being slidable along respective ways in a direction transverse to the longitudinal axis of said heating element and toward and away from said first wall and assembled with the ways from the opening into said channel member, said ways holding said bodies in spaced relation, the connection between a body and the respective end of said heating element including a resilient member effecting a pull on the element end to maintain the element under tension when said bodies are assembled on respective ways, the foregoing construction permitting said bodies and said heating element to be moved as a subassembly to and from assembly with said housing.

9. The construction of claim 8 wherein each way is formed of spaced portions in side-by-side relation and disposed between said second walls, and wherein said bodies span the portions aforesaid of respective ways.

10. A baseboard heater assembly, comprising a main housing provided by an elongated channel member whose web portion forms a first wall and whose flange portions form a laterally spaced second walls projecting from one side of said first wall, a terminal housing at each end of said main housing for closing the ends thereof, each terminal housing having a wall disposed within said main housing and disposed adjacent to a respective end thereof, a flexible electric heating element disposed within said main housing, and a dielectric body at each end of said element and having connection therewith, each of said bodies having a sliding connection with way means formed on the respective walls of said terminal housings so that said bodies and said heating element may be slid as a subassembly to and from assembled relation with said housing, and the connection between at least one dielectric body and its element end including resilient means which exert a tension on said element to maintain it taut when said dielectric bodies have been moved to assembled position on said housing.

11. The construction of claim wherein said terminal housing walls are each slotted to provide spaced way portions in side-by-side relation adjacent respective main housing member second walls, and wherein said bodies span the way portions aforesaid of respective terminal housing walls.

12. The construction of claim 11 wherein said main housing member first wall provides loop members and wherein said terminal housings provide tongue members closely fitting within respective loop members to limit movement of said terminal housings in a direction toward each other under the force exerted by said tensioned element and to limit terminal housing movement in a direction flatwise of said main housing member first wall.

13. A baseboard heater assembly, comprising a main housing provided by an elongated channel member whose web portion forms a first wall and whose flange portions from laterally spaced second walls projecting from one side of said first wall, a terminal housing at each end of said main housing for closing the same and each having inner and outer walls spaced longitudinally of said main housing, a flexible elongated electric heating element connected between respective terminal housing inner walls and including resilient means for establishing a tension on said element to maintain it taut, loop members on said Web portion and tongue members, on said terminal housings closely fitting within respective loop members for limiting movement of said terminal housings in a direction fiatwise of said Web and toward each other.

14. A baseboard heater assembly, comprising a horizontally elongated housing having an upright rear Wall and a forwardly projecting top wall and also having means at its lower portion to admit air to be heated and means at its upper portion for discharge of heated air, an elongated heating element within said housing and disposed below said top wall, said heating element being adapted to be connected to a source of electrical energy, an elongated, bottomless plenum chamber within said housing and disposed above and generally coextensive with said heating element, said plenum chamber being in part formed by a wall depending from said top wall and spaced forwardly of said rear wall, and a thermally responsive device Within said chamber positioned intermediate the ends thereof, said responsive device being in electrical circuit with said heating element and adapted to reduce heat output of said element upon excessive temperature rise within said plenum chamber.

15. The construction of claim 14 wherein said depending wall cooperates with said top wall and said rear wall to provide said plenum chamber, and wherein said depending wall is removably secured within said housing.

16. The construction of claim 15 wherein forward-1y facing abutment means is provided by said housing, wherein said depending wall is seated against said abutment means, and wherein a bracket is removably secured to said housing rear wall and has a portion bearing against a forwardly facing portion of said depending wall to removably retain the latter in position against said abutment means.

17. The construction of claim 16 wherein interfitting tongue and slot means are in part provided by said bracket and in part provided by said housing rear wall for removably securing said bracket to said housing.

18. The construction of claim 16 wherein a forwardly projecting, lanced out portion of said housing rear wall provides a slot and wherein said bracket has a tongue closely fitting within said slot for removably securing said bracket to said housing.

19. The construction of claim 16 and further comprising means providing a wireway disposed at the bottom of said housing rear wall, said bracket having another portion bearing against such means to removably retain the latter in position within said housing.

20. A baseboard heater assembly, comprising an elongated housing, an elongated electric heating element mounted in said housing between longitudinally spaced parts thereof, a support on said housing forming one of said parts and having a slot therein, a helical spring mechanically and electrically connected at one end to an of said element and stretched in the direction of its axis between said element and said support, the other end of said heating element being connected to the other of spaced parts and the other end of said helical spring being formed with a loop disposed in a plane generally normal to the spring axis, said loop projecting through said support slot, and lead connections for connecting said heating element to an electrical power circuit, one of said lead connections having a conductor portion extending through said spring loop and disposed across said slot and maintained in position by the pressure exerted thereagainst by said spring to prevent unintentional withdrawal of said spring loop through said slot and to thus establish an electrical power circuit connection through said spring.

21. The construction of claim 20 wherein said support is a dielectric body which is removably carried by said housing.

22. A baseboard heater assembly, comprising a horizontally elongated housing having one side open to admit air into a lower portion thereof and to discharge heated air out of an upper portion thereof, an elongated heated element within said housing and disposed below the upper portion thereof, an elongated heating element within said housing and disposed below the upper portion thereof, said heating element being adapted to be connected to a source of electrical energy, an elongated plenum chamber within said housing and disposed above and generally coextensive with said heating element, said plenum chamber being open only at the bottom for entrance and exit of air thereinto, and a thermally responsive device within said chamber positioned intermediate the ends thereof, said responsive device being in electrical circuit with said heating element and adapted to reduce heat output of said element upon an excessive temperature rise within said plenum chamber.

23. A baseboard heater assembly, comprising an elongated housing having one side open to admit cool air into lower portion thereof and to discharge heated air out of the upper portion thereof, a heating element within said housing and disposed below the upper portion thereof, said heating element being adapted to be connected to a source of electrical energy, an elongated plenum chamber within said housing and disposed above and generally coextensive with said heating element, said plenum chamber being open only at the bottom to provide a mouth for entrance of air thereinto and the air within said chamber being substantially stagnant so long as air rises uniformly along said heating element because such uniformly rising air exerts a uniform pressure at said chamber mouth along the entire chamber length, and a thermally responsive device within said chamber positioned intermediate the ends thereof, said device being in electrical circuit with said heating element and adapted to reduce heat output of said element upon an excessive temperature rise within said plenum chamber upon flow of heated air into said chamber caused by non-uniform flow of rising air resulting from a partial blockage of air flow into or out of said housing due to the presence of an air flow-impeding object thereadjacent.

(References on following page) 3,305,665 2/1967 Laing 219-370 References Clted FOREIGN PATENTS UNITED STATES PATENTS 972,074 M1950 France 3/1920 Colby 1 338--282 X 1,230,451 4/1960 France. 12/1941 Wilson et a1. 219375 X 5 489,850 8/1938 Great Britain.

11/1959 Balestrini 338-282 X 11/1961 Doehler 219 375 ANTHONY BARTIS, Pnmary Exammer 2/1954 Spurr 219-377 8/ 1962 Knoll et a1 2193 65 6/1965 Jepson et a1 219477 10 219 -342, 363, 375, 377, 541, 542; 338-282, 316 

